每日一问第1期 | 截取字符串

package com.albertyy.AlbertYang;

import java.util.Scanner;

public class String_Substitution {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    String str = sc.nextLine();
    System.out.println(substitutionStr(str));
  }

  public static String substitutionStr(String str) {
    char[] c = str.toCharArray();
    for (int i = 0; i < c.length; i++) {
      if ('a' <= c[i] && c[i] <= 'z') {
        c[i] = Character.toUpperCase(c[i]);
      } else if ('A' <= c[i] && c[i] <= 'Z') {
        c[i] = Character.toLowerCase(c[i]);
      }
    }
    String s = new String(c);
    return s;
  }

}

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);        
        String str1 = sc.nextLine();
        System.out.println(changeStr(str1));        
    }
    public static String changeStr(String str){  
        char[] ch = str.toCharArray();          
        int a = 'A'-'a';   //获得大小写之间差值  
        for(int i = 0; i < ch.length; i++){  
            if('a' <= ch[i] && ch[i] <= 'z'){  
                ch[i] = (char)(ch[i]+a);  
            }else if('A' <= ch[i] && ch[i] <= 'Z'){  
                ch[i] = (char)(ch[i]-a);  
            }           
        }  
          String s=new String(ch);
        return s;  
    }  
}